Selected hematology ratios in cats with non-septic effusions highly suspected of feline infectious peritonitis

In veterinary medicine, knowledge about hematologic ratios (neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) and mean platelet volume-to-platelet ratio (MPV/PLT)) is limited, particularly in cats. While the roles of these ratios have been proven in oncology, systemic inflammation with or without systemic inflammatory response syndrome (SIRS), and sepsis, information is lacking about their alterations in non-septic effusions, like feline infectious peritonitis (FIP). This study aimed to describe whether NLR, PLR, and MPV/PLT were changed and whether they correlated with routine hematologic and biochemical parameters in 16 cats with non-septic effusions, highly suspected to be the effusive form of FIP without SIRS, compared to nine clinically healthy cats. The NLR was calculated as the absolute count of neutrophils divided by the absolute count of lymphocytes, PLR by calculating the absolute platelet divided by the absolute lymphocyte count, and MPV/PLT by dividing mean platelet volume by absolute platelet count. The NLR, MPV, and MPV/PLT ratios were higher in cats with non-septic effusions suspected to be FIP, but PLR did not differ, when compared to healthy cats. Correlation analysis did not show any association between the selected ratios and hematological and biochemical parameters. In the absence of leukocytosis, increased NLR could help us to confirm the presence of systemic inflammation in cats with non-septic effusions indicative of FIP. However, a high MPV/PLT ratio should be interpreted with caution, especially in cats